igneous

Diorite

Diorite (an intrusive igneous rock)

Hardness: 6-7 Mohs; Color: Salt and pepper (mottled black and white); Luster: Sub-vitreous to dull; Structure: Phaneritic (coarse-grained); Cleavage: Distinct in feldspar and amphibole minerals; Specific Gravity: 2.8-3.0.

Hardness: 6-7 Mohs
Color: Salt and pepper (mottled black and white)
Luster: Sub-vitreous to dull

Identified February 5, 2026More igneous →

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Physical properties

Formation & geological history

Formed through the slow cooling of silicate magma below the Earth's surface (intrusive), typically in volcanic arcs and mountain-building zones (subduction zones). It consists of plagioclase feldspar, biotite, and hornblende.

Uses & applications

Used primarily as a decorative stone in architecture and construction, such as floor tiles, countertops, and paving. Historically used by ancient civilizations for sculpture due to its extreme durability.

Geological facts

The Code of Hammurabi was inscribed on a massive basaltic-diorite stele. It is often referred to as salt and pepper rock because of its distinct mineral speckling.

Field identification & locations

Identify by its coarse grain and lack of visible quartz compared to granite. Found in large mountain ranges like the Andes or Alps. Collectors should look for balanced mineral distribution.

Other igneous specimens

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Blue Apatite

Fluorapatite (Ca5(PO4)3F)

mineral

Dark Igneous Rock (Likely Basalt or Diabase)

Basalt (extrusive igneous rock) or Diabase (intrusive igneous rock - also known as Dolerite), largely composed of plagioclase feldspar, pyroxene (augite), and sometimes olivine and amphibole. Exact mineralogy would require thin section analysis.

Igneous